Gearlike rolling motion mediated by commensurate contact: Carbon nanotubes on HOPG

We report on experiments in which multiwall carbon nanotubes (CNT’s) are manipulated with atomic force microscopy (AFM) on a graphite highly oriented pyrolytic graphite (HOPG) substrate. We find certain discrete orientations in which the lateral force of manipulation dramatically increases as we rotate the CNT in the plane of the HOPG surface with the AFM tip. The threefold symmetry of these discrete orientations indicates commensurate contact of the hexagonal graphene surfaces of the HOPG and CNT. As the CNT moves into commensurate contact, we observe the motion change from sliding/rotating in-plane to stick-roll motion.